US Sen. John Cornyn,R-TX,, questions US Supreme Court Nominee Sonia Sotomayor on July 16, 2009 during the fourth day of confirmation hearings before the Senate Judiciary Committee on Capitol Hill in Washington, DC. AFP PHOTO/Karen BLEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)

Photo: Karen Bleier, AFP/Getty Images

US Sen. John Cornyn,R-TX,, questions US Supreme Court Nominee Sonia...

The gun-rights lobby suffered a rare setback in Congress on Wednesday when the Senate narrowly rejected a plan to allow Americans to carry concealed firearms across state lines if they were legally allowed to carry the weapons in their home states.

Two Republican defections sealed the defeat for gun advocates, who fell two votes short of the 60 needed under Senate rules to adopt the amendment. Thirty-nine senators, including Republicans Richard Lugar of Indiana and George Voinovich of Ohio, voted to kill the measure that Sen. John Thune, R-S.D., tried to tack on as an amendment to a defense spending bill.

Gillibrand and other foes said the Thune proposal would undermine states' rights to enact tough concealed-carry laws. She warned that people who are barred by some state laws from qualifying for concealed-carry permits could "shop around for a lower standard in other states."

"It is simply wrong for the federal government to overrule a state's ability to enact reasonable, constitutional gun laws designed to prevent criminals and other violent and dangerous persons from carrying guns in city streets," Gillibrand said.

Sen. John Cornyn, R-Texas, a co-sponsor of the proposal, blamed Senate Democrats and President Obama for the defeat. He said the proposal "would allow law-abiding" citizens with concealed-weapons permits "to protect themselves while traveling to other states."

"I'm disappointed with this move and certainly hope it is not a sign of things to come," Cornyn said. "The Second Amendment guarantees law-abiding citizens the fundamental right to bear arms, and Congress should be working to defend, not weaken, these constitutional rights."

Thune contended that his proposal was needed to guarantee that legal gun owners can carry their firearms and use them when they feel it is needed - even when traveling to other states. The South Dakota senator said his constituents traveling to New York City's Central Park would find it "a much safer place" if they were permitted to hide their pistols.

The measure was strongly supported by the NRA and the Gun Owners of America, which in recent years have won a string of votes loosening restrictions on weapons with a coalition of Republicans and rural Democrats. Forty-eight states allow concealed weapons to be carried by lawful owners, but senators from some states with tough restrictions - including California and New York - said the Thune proposal would have overturned their curbs on spouse abusers and alcoholics or gun-safety training requirements.

Sen. Dianne Feinstein, D-Calif., called Wednesday's vote "a great victory for public safety and the American people."

"But we must remain vigilant," Feinstein added. "The gun lobby and its supporters in Congress will be back, looking for additional legislative vehicles by which to eviscerate our nation's common-sense gun laws. We must continue to fight them and their ill-conceived efforts at every turn."